Re: [RFC V7 1/3] libxl domain snapshot introduction

[Ian Campbell <Ian.Campbell@citrix.com>]

On Fri, 2014-10-10 at 16:48 +0800, Chunyan Liu wrote:
> Domain snapshot includes disk snapshots and domain state saving. domain
> could be resumed to the very state when the snapshot was created. This
> kind of snapshot is also referred to as a domain checkpoint or system
> checkpoint.

Are these checkpoints considered consistent?

> 
> Disk snapshot is crash-consistent if the domain is running.

Did you mean inconsistent here?

>  To libxl,
> even domain is paused, there is no data flush to disk operation. So, for
> active domain (domain is started), take a disk-only snapshot and then
> resume, it is as if the guest had crashed. For this reason, we only
> support disk-only snapshot when domain is inactive (like: libvirt defines
> but not start the domain.)
> 
> Disk snapshot itself could be "internal" (like in qcow2 format, snapshot
> and delta are both in one image file), or "external" (snapshot in one file,
> delta in another).
> 
> Expected 4 types of operations:
> 
> "domain snapshot create":
>     means saving domain state (if not disk-only) and doing disk snapshots.
> 
> "domain snapshot revert":
>     means rolling back to the state of indicated snapshot.

This operation is only possible on what you call a "checkpoint" in the
first paragraph. is the right?

> 
> "domain snapshot delete":
>     delete indicated domain snapshot.
> 
> "domain snapshot list":
>     list domain snapshot information.